| | SLO | ENG | Cookies and privacy

Bigger font | Smaller font

Search the digital library catalog Help

Query: search in
search in
search in
search in
* old and bologna study programme

Options:
  Reset


1 - 3 / 3
First pagePrevious page1Next pageLast page
1.
An effect of sodium dodecylsulfate on the corrosion of copper in sulphuric acid media
Regina Fuchs-Godec, Valter Doleček, 2004, original scientific article

Abstract: The effect of sodium dodecylsulfate (SDS) on copper corrosion in a solution of 0.5 M H2SO4 + x M SDS was studied using electrochemical polarisation measurements. The critical micelle concentration (CMC) of SDS in 0.5 M H2SO4 is 8 * 10-4 M, and the experimental concentrations of SDS were in the range below and above the CMC. It was found that SDS is a good anodic inhibitor at lower anodic overpotentials, i.e. very close to the rest potential. Adsorptionof the inhibitor obeys the Langmuir isotherm. Plots of log [▫$theta$▫/(1-▫$theta$▫)] versus log ▫$c_{inh}$▫ yielded straight lines with a slope change at the CMC. Accordingly, the CMC could be determined from these electrochemical measurements. The values of ▫$Delta$▫▫$G_{ads}$▫ calculated from the Langmuir plots are negative, suggesting that the inhibitive action of SDS in 0.5 M H2SO4 results from the electrostatic adsorption of C12H25SO4- ions onto the positively charged copper surface.
Keywords: electrochemistry, corrosion inhibitors, surfactants, potentiodynamic polarisation, corrosion kinetic parameters, copper, Langmuir isotherm, critical micelle concentration, sulphuric acid
Published in DKUM: 01.06.2012; Views: 1835; Downloads: 107
URL Link to full text

2.
Inhibitory effect of non-ionic surfactants of the TRITON-X series on the corrosion of carbon steel in sulphuric acid
Regina Fuchs-Godec, 2007, original scientific article

Abstract: The corrosion inhibition characteristics of non-ionic surfactants of the TRITON-X series, known as TRITON-X-100 and TRITON-X-405, on stainless steel (SS) type X4Cr13 in sulphuric acid were investigated by potentiodynamic polarisation measurements. It was found that these surfactants act as good inhibitors of the corrosion of stainless steel in 2 mol L-1 H2SO4 solution, but the inhibition efficiency strongly depends on the electrode potential. Thepolarisation data showed that the non-ionic surfactants used in this study acted as mixed-type inhibitors and adsorb on the stainless steel surface, in agreement with the Flory-Huggins adsorption isotherm. Calculated Gads values are -57.79 kJ mol-1 for TRITON-X-100, and -87.5 kJ mol-1 for TRITON-X-405. From the molecular structure it can be supposed that these surfactants adsorb on the metal surface through two lone pairs of electrons on the oxygen atoms of the hydrophilic head group, suggesting a chemisorption mechanism.
Keywords: electrochemistry, corrosion inhibitors, non-ionic surfactants, Flory-Huggins isotherm, critical micelle concentration, sulphuric acid
Published in DKUM: 01.06.2012; Views: 2076; Downloads: 104
URL Link to full text

3.
The adsorption, CMC determination and corrosion inhibition of some N-alkyl quaternary ammonium salts on carbon steel surface in 2 M H2SO4
Regina Fuchs-Godec, 2006, original scientific article

Abstract: Electrochemical measurements were performed to investigate the effectiveness of cationic surfactants of the N-alkyl quaternary ammonium salt type, i.e. myristyltrimethylammonium chloride (MTACl), cetyldimethylbenzylammonium chloride (CDBACl), and trioctylmethylammonium chloride (TOMACl), as corrosion inhibitors for type X4Cr13 ferritic stainless steel in 2 M H2SO4 solution. Potentiodynamic polarization measurements showed that these surfactants hinder both anodic and cathodic processes, i.e. act as mixed-type inhibitors. It was found that the adsorption of the N-alkyl ammonium ion in 2 M H2SO4 solution follows the Langmuir adsorption isotherm. Plots of log ▫$[/theta$▫/(1-▫$/theta$▫)] versus log▫$c_{inh}$▫ yielded straight lines with a slope, which changed drasticallyat the critical micelle concentration (CMC) of the surfactants studied. Accordingly, the CMC could be accurately determined from these measurements. The calculated values of the free energy of adsorption ▫$/Delta$▫▫$G_{ads}$▫ are, in cases when the charge on the metal surface is negative with respect to the PZC, relatively high what is characteristically for the chemisorption. On the other hand, for positive metal surfaces it is assumed that ▫$SO_4^{2-}$▫ anions are adsorbed first, so the cationic species would be limited by the surface concentration of anions. Accordingly ▫$/Delta$▫▫$G_{ads}$▫ values were lower in this case and the adsorption is due to merely electrostatic attraction, which is characteristically of physisorption.
Keywords: electrochemistry, corrosion inhibitors, cationic surfactants, Langmuir isotherm, corrosion kinetic parameters, critical micelle concentration, sulphuric acid
Published in DKUM: 30.05.2012; Views: 2733; Downloads: 105
URL Link to full text

Search done in 0.11 sec.
Back to top
Logos of partners University of Maribor University of Ljubljana University of Primorska University of Nova Gorica